Condensed Consolidating Financial Information - Statements of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Condensed Consolidating Financial Information
Revenue	$ 2,053us-gaap_Revenues	$ 1,609us-gaap_Revenues
Costs and Expenses:
Network Access Costs	723lvlt_NetworkAccessCosts	614lvlt_NetworkAccessCosts
Network Related Expenses	356lvlt_NetworkRelatedExpenses	292lvlt_NetworkRelatedExpenses
Depreciation and Amortization	288	184
Selling, General and Administrative Expenses	370	255
Total Costs and Expenses	1,737us-gaap_CostsAndExpenses	1,345us-gaap_CostsAndExpenses
Operating Income (Loss)	316us-gaap_OperatingIncomeLoss	264us-gaap_OperatingIncomeLoss
Other Income (Expense):
Interest Income	1us-gaap_InterestIncomeOther	0us-gaap_InterestIncomeOther
Interest expense	(180)us-gaap_InterestExpense	(151)us-gaap_InterestExpense
Interest income (expense) affiliates, net	0lvlt_InterestIncomeExpenseAffiliatesNet	0lvlt_InterestIncomeExpenseAffiliatesNet
Equity in net earnings (losses) of subsidiaries	0	0
Other, net	(10)lvlt_NonoperatingIncomeExpenseOther	6lvlt_NonoperatingIncomeExpenseOther
Total Other Expense	(189)lvlt_OtherIncomeExpense	(145)lvlt_OtherIncomeExpense
Income (Loss) before Income Taxes	127	119
Income Tax Expense	(5)us-gaap_IncomeTaxExpenseBenefit	(7)us-gaap_IncomeTaxExpenseBenefit
Net Income (Loss)	122us-gaap_NetIncomeLoss	112us-gaap_NetIncomeLoss
Other Comprehensive Income (Loss), Net of Income Taxes	(141)	6
Comprehensive Income (Loss)	(19)us-gaap_ComprehensiveIncomeNetOfTax	118us-gaap_ComprehensiveIncomeNetOfTax
Level 3 Communications, Inc.
Condensed Consolidating Financial Information
Revenue	0	0
Costs and Expenses:
Network Access Costs	0	0
Network Related Expenses	0	0
Depreciation and Amortization	0	0
Selling, General and Administrative Expenses	1	0
Total Costs and Expenses	1	0
Operating Income (Loss)	(1)	0
Other Income (Expense):
Interest Income	0
Interest expense	(19)	(34)
Interest income (expense) affiliates, net	333	288
Equity in net earnings (losses) of subsidiaries	(191)	(142)
Other, net	0	0
Total Other Expense	123	112
Income (Loss) before Income Taxes	122	112
Income Tax Expense	0	0
Net Income (Loss)	122	112
Other Comprehensive Income (Loss), Net of Income Taxes	(141)	6
Comprehensive Income (Loss)	(19)	118
Level 3 Financing, Inc.
Condensed Consolidating Financial Information
Revenue	0	0
Costs and Expenses:
Network Access Costs	0	0
Network Related Expenses	0	0
Depreciation and Amortization	0	0
Selling, General and Administrative Expenses	0	0
Total Costs and Expenses	0	0
Operating Income (Loss)	0	0
Other Income (Expense):
Interest Income	0
Interest expense	(155)	(112)
Interest income (expense) affiliates, net	501	459
Equity in net earnings (losses) of subsidiaries	(536)	(488)
Other, net	0	0
Total Other Expense	(190)	(141)
Income (Loss) before Income Taxes	(190)	(141)
Income Tax Expense	(1)	(1)
Net Income (Loss)	(191)	(142)
Other Comprehensive Income (Loss), Net of Income Taxes	0	0
Comprehensive Income (Loss)	(191)	(142)
Level 3 Communications, LLC
Condensed Consolidating Financial Information
Revenue	818	737
Costs and Expenses:
Network Access Costs	320	290
Network Related Expenses	230	182
Depreciation and Amortization	74	70
Selling, General and Administrative Expenses	247	143
Total Costs and Expenses	871	685
Operating Income (Loss)	(53)	52
Other Income (Expense):
Interest Income	0
Interest expense	(1)	(1)
Interest income (expense) affiliates, net	(766)	(712)
Equity in net earnings (losses) of subsidiaries	177	178
Other, net	2	3
Total Other Expense	(588)	(532)
Income (Loss) before Income Taxes	(641)	(480)
Income Tax Expense	0	(1)
Net Income (Loss)	(641)	(481)
Other Comprehensive Income (Loss), Net of Income Taxes	0	0
Comprehensive Income (Loss)	(641)	(481)
Other Non-Guarantor Subsidiaries
Condensed Consolidating Financial Information
Revenue	1,287	931
Costs and Expenses:
Network Access Costs	455	383
Network Related Expenses	126	110
Depreciation and Amortization	214	114
Selling, General and Administrative Expenses	122	112
Total Costs and Expenses	917	719
Operating Income (Loss)	370	212
Other Income (Expense):
Interest Income	1
Interest expense	(5)	(4)
Interest income (expense) affiliates, net	(68)	(35)
Equity in net earnings (losses) of subsidiaries	0	0
Other, net	(12)	3
Total Other Expense	(84)	(36)
Income (Loss) before Income Taxes	286	176
Income Tax Expense	(4)	(5)
Net Income (Loss)	282	171
Other Comprehensive Income (Loss), Net of Income Taxes	(141)	6
Comprehensive Income (Loss)	141	177
Eliminations
Condensed Consolidating Financial Information
Revenue	(52)	(59)
Costs and Expenses:
Network Access Costs	(52)	(59)
Network Related Expenses	0	0
Depreciation and Amortization	0	0
Selling, General and Administrative Expenses	0	0
Total Costs and Expenses	(52)	(59)
Operating Income (Loss)	0	0
Other Income (Expense):
Interest Income	0
Interest expense	0	0
Interest income (expense) affiliates, net	0	0
Equity in net earnings (losses) of subsidiaries	550	452
Other, net	0	0
Total Other Expense	550	452
Income (Loss) before Income Taxes	550	452
Income Tax Expense	0	0
Net Income (Loss)	550	452
Other Comprehensive Income (Loss), Net of Income Taxes	141	(6)
Comprehensive Income (Loss)	$ 691	$ 446

The amount of income (loss) from equity investment in subsidiaries.

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The net amount of operating interest income (expense) from affiliates.

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Network Access Costs for the communications business includes leased capacity, right-of-way costs, access charges, satellite transponder lease costs and other third party costs directly attributable to providing access to customer locations from the Level 3 network, but excludes Network Related Expenses, employee expenses, depreciation and amortization and related impairment expenses.

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Network Related Expenses includes certain expenses associated with the delivery of services to customers and the operation and maintenance of the Level 3 network, such as facility rent, utilities, maintenance and other costs, as well as salaries, wages and related benefits (including non-cash stock-based compensation expenses) associated with personnel who are responsible for the delivery of services, operation and maintenance of its communications network, but excludes depreciation and amortization.

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The net amount of other income and expense amounts, components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period.

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Other Income Expense

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Total costs of sales and operating expenses for the period.

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the cost of borrowed funds accounted for as interest expense.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The net result for the period of deducting operating expenses from operating revenues.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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